Chip, filter, de-cat and some cams might get you to 170 or thereabouts depending on who's roolers your using

Get any decent power from a N/A car is nearly always going to cost more per BHP then on a turbo'd engine.

To get over 200BHP from this engine you will need head work, cams, throttle bodies, increased rev limit and management, fitting a 2.3 bottom end will make this slightly more easier

OR

Turbo the 2.3 and make some real power

Not cheap though, is any turbo car? but the 2.3 responds well to forced induction and many of the Cosworth owners dream of having a 2.3 Turbo in their rep mobiles

Chap in our group had a 2.3 Turbo making 300bhp and 360lb/ft @12psi with more to come if only the RS2000's 4x4 transfer box gears where not made out of crackers! Just dont ask how much it all cost him though!

Another point of note is that Cosworth* developed the 2.3 for Ford, so you may well Badge it up Cosworth if your brave enough!!

*Ref Grahame Robson in one of his books